FIG. 1 is a block diagram of a storage area network (SAN) system 10. The SAN system 10 includes a host 12, a network 14, a storage server 16, and a storage system 18. The host 12 generally includes a computer that may be further connected to other computers via the network 14 or via other connections. The network 14 may be any type of computer network, such as a TCP/IP network, an Ethernet network, a token ring network, an asynchronous transfer mode (ATM) network, a Fibre Channel network, etc. The storage system 18 may be any type of storage system, such as a disk, disk array, RAID (redundant array of inexpensive disks) system, etc.
The storage server 16 generally transparently connects the host 12 to the storage system 18. More specifically, the host 12 need only be aware of the storage server 16, and the storage server 16 takes responsibility for interfacing the host 12 with the storage system 18. Thus, the host 12 need not be aware of the specific configuration of the storage system 18. Such an arrangement allows many of the storage management and configuration functions to be offloaded from the host.
Such offloading allows economies of scale in storage management. For example, when the storage system 10 has multiple hosts on the network 14 and the components of the storage system 18 are changed, all the hosts need not be informed of the change. The change may be provided only to the storage server 16.
Similar concepts may be applied to other storage system architectures and arrangements such as networked attached storage (NAS), etc.
One concern with storage servers is that data not be dropped. However, if the storage server 16 fails to adequately monitor congestion, the storage server 16 may become overloaded and have to drop new data in order to continue processing the existing data. Such dropped data results in increased network traffic because the host may be required to re-submit storage requests that were dropped.
It is a goal of the present invention to reduce the need to drop data when the data is being processed by a storage server.